Various types of halogen incandescent lamps are used in the automotive industry. It is well known to make halogen incandescent lamps of quartz glass, for example to make such lamps for head lights, fog lights, driving lights and the like. For certain applications, for example for motor cycles, lamps are required which are particularly resistant to shock and vibration, and especially resistant to vibrations which might induce resonance effects within the lamp. It has been proposed to improve the internal structure of the lamp, which includes the filaments and, in a dual-filament lamp, a light shielding cap, by anchoring one of the current supply leads directly in the quartz glass--see, for example, the referenced German Patent Disclosure Document Nos. DE-OS 24 00 315 and 28 40 537. The lamps there disclosed utilize quartz glass, in which the current supply lead which also carries the light shielding cap is embedded. This is possible because of the extremely small thermal coefficient of expansion of quartz. A current supply lead which is directly connected into, for example by being melted into, a tipped-off end of the lamp, used first to evacuate the lamp, then fill the lamp with a fill gas and, tipping it off, may bend during operation of the lamp due to thermal expansion of the current supply lead. The current supply lead need not be melted into the lamp; it may only engage the internal glass wall of the lamp. Bending of the current supply lead, however, deflects the filament from the optical axis, and from perfect alignment therewith. Additionally, it has been found that thermal and mechanical stresses arise particularly, if the current supply lead is melted into the tipped-off end of the lamp. The current supply lead expands due to the operating temperature of the lamp. If the thermal expansion of the current supply lead is excessive, the bulb or envelope of the lamp may form cracks which lead to sealing losses, and eventually destruction of the lamp.
It is desirable to make lamps, particularly lamps for automotive use, not of the very expensive quartz glass but, rather, of hard glass. Hard glass also eliminates the necessity to use the expensive molybdenum foil connection in a press or pinch seal, which is required in quartz glass. Such molybdenum foils are expensive. Molybdenum foils need not be used with lamps made of hard glass--see, for example, the referenced U.S. Pat. Nos. 4,178,050, Kiesel et al; 4,302,698, Kiesel et al; 4,305,016, Schmidt, all assigned to the assignee of the present application. The thermal coefficient of expansion of the hard glasses which are used is about 10 times as high as that of the quartz glass. It is, therefore, not possible to construct lamps in the aforementioned manner which are stable internally, that is, in which the electrode assembly is not subject to vibration or oscillations, and particularly oscillations which might result in resonance, upon being subjected to shock or vibration when installed in a motor vehicle.